http://www.raven-games.com/hosted/newhexen/

After nearly a year in development, this source port of Hexen II has finally come out. New in this release (straight up cut and paste):

Underwater Caustics!
Now you can enjoy beutiful underwater caustics as light refracts through the water's surface and creates beutiful patterns on underwater surfaces!!

Detail Texturing
Closeup no texture ever looks good, they are abit "blurry". So now by using the following CVAR on the console you can change this! "r_detail 0/1" This turns detail texturing off/on... the default value is 1.

Gamma OH YEAH!
Yes, you heard right, NewHexen now supports working Gamma!! Use the following CVAR on the console to set it to your preferred level: "gamma 1". The gamma CVAR ranges from 0.2 (brightest) to 1 (darkest)... the default value is 1.

External Texture support!
The engine now supports external texture loading! Now you can play your own custom Hexen2 maps in all its true color glory using TGA files!

Larger than Life levels!!
NewHexen now sports with upgraded level design limits!!! You heard right, all the limits have been pushed to that of the Quake2 standard. What size you can build in Quake2, you can now do with NewHexen!! Note that any level that exceeds the original limits wont be able to run the level under non-NewHexen versions.